A wide range of radioactive waste processes are known for the isolation of a variety of low level wastes (LLW) and intermediate level wastes (ILW) by the use of volume reduction, and solidification. The resulting product of these processes, which may be substantially uncontaminated, slightly contaminated, or remain highly contaminated, is then usually packaged in drums or other containers for disposal.
Ideally, radioactive waste should be as substantially reduced in volume as is commercially practical due to the excessively high costs of disposal or storage. Typically, this is accomplished by tight packing into containers such as metal drums or the like. Such containers suffer from various disadvantages including the fact that they are usually round and therefore a considerable amount of storage space is lost due to the dead space between the containers. Additionally, such containers are known to bulge or corrode over time.
One improved method of reducing the volume of radioactive waste is uniaxial centrifugal casting thereof as is disclosed in U.S. Pat. No. 4,897,221 issued Jan. 30, 1990 to Frank Manchak, Jr.
Other uniaxial centrifugal waste casting methods are disclosed in U.S. application Ser. No. 328,020 filed Mar. 23, 1989 by Frank Manchak, Jr., et al, and in U.S. application Ser. No. 384,087 filed as a CIP of Ser. No. 328,020 on Jul. 21, 1989. These applications both disclose the use of reinforcing cages which are used in the casting mold.
It is now suspected, although not scientifically proven, that high density packing of radioactive waste not only reduces the volume to be stored, but also that such high density packing also provides greater inherent radiation shielding and reduced radiation leakage as compared to less dense packing. For some radioactive materials, high density packing is also suspected to reduce the radioactive half life, i.e., enhance the rate of radioactive decay.
A high density packing process and apparatus is desired so that hazardous radioactive waste can be more densely and rapidly compacted into a radiation shielded dense monolithic form having strength and structural integrity for transport and which can be monitored for radiation compliance and, if necessary, provided with additional radiation barrier material before leaving the centrifugal casting apparatus.
As referred to herein, the term "castable radioactive materials" is meant to comprise a hardenable mixture of radioactive waste materials and other waste materials mixed as necessary with one or more hardenable materials such as polyorganic compounds or cementitious materials or the like.
As used herein, the terms "monolith", "cast monolith" and "monolithic form" are intended to refer to a solidified casting having one or more layers of radiation encapsulating material on the exterior thereof. Such monoliths may be provided, as taught herein, either by casting the entire monolith including shell layers of impact resistant and radiation shielding materials and the hazardous waste at the jobsite or, in the alternative, by using pre-formed shells and merely casting the waste at the jobsite. In pre-formed shells are used, provision must be made for casting additional radiation barrier material inside of the pre-formed shells if jobsite conditions dictate.